Isolation and characterization of a bacteriophage capable of combatting Shiga Toxin-Producing E. coli O157:H7

Document Type : Original Article

Authors

1 Botany and microbiology department,Faculty of science,Zagazig University

2 Botany and Microbiology Department, Faculty of Science, Zagazig University

3 aDepartment of Botany and Microbiology, Faculty of Science, Zagazig University, Egypt

Abstract

The study aimed to identify and analyze a bacteriophage from the Al.Qnayat Wastewater Treatment Plant in EL-Sharika Governorate. A distinctive lytic zone in the bacterial lawn from a plaque assay indicated its presence. Successfully, a novel phage, Vb-Ecm1, was isolated using a phage spot test, demonstrating strong lytic properties against Shiga toxin-producing E. coli (STEC) O157 strains LC666912 (stx2) and LC666913 (stx1/stx2). Electron microscopy identified the phage's structural features, hinting at its belonging to the Myoviridae family due to its extended contractile tail. Vb-Ecm1 produced a distinct 1mm plaque with a transparent core. Its host specificity was assessed using spot tests on a variety of bacterial strains from Egyptian labs. Remarkably, Vb-Ecm1 exhibited potent lytic activity against the E.coli strain LC589615, sourced from Ainshams University's Botany department. The phage's adsorption rate showed a consistent decrease, bottoming out at 12 minutes, suggesting an adsorption rate of K=1.7x10-10. The phage infection lifecycle was detailed through a one-step growth curve, revealing 10-minute latency and an average burst size of 128 for Vb-Ecm1. Vb-Ecm1 displayed notable heat stability, remaining active up to 50°C. However, it became inactive at 80°C and completely lost its activity at 90°C. Its activity spanned a wide pH spectrum (4 to 11), with optimal survival observed at pH 6 and 7.8. Notably, the phage was more resilient at a pH of 6 compared to a pH of 8.

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